This example uses React and D3 v7 to render a single SVG circle that follows the mouse cursor. The circle’s center coordinates are updated via React state on every mouse move event, using the `onMouseMove` handler. The code leverages D3’s `arc` module and React’s `useState` hook, with a fixed canvas size of 960 by 500 pixels. The result is an interactive smiley face that tracks pointer movement in real time.